1. Field of the Invention
The present invention relates to an automatic automotive air conditioner and more specifically to a mode switching arrangement for such an air conditioner.
2. Description of the Prior Art
In order to reduce driver distraction and to improve driving safety, it is has been proposed to use automatic air conditioners in automotive vehicles. These devices are arranged so as to only require the desired temperature to inputted. Once provided with this data input, these automatic type of air conditioners are capable of automatically controlling the temperature to which the conditioned air is adjusted, the ON/OFF control of the compressor, the setting of the doors which control the vent mode, the internal air temperature selection, the amount of air driven by the fan, etc., without further intervention each time the engine ignition switch is closed.
An example of such an arrangement is disclosed in Nissan Service Manual No. 578 which was published in June of 1987. This arrangement includes a number of different sensors which are arranged to sense the internal and external air temperatures, the heating effect of external sunshine entering the vehicle cabin, and like. These sensors enable the various decisions which must be made in order to achieve the required control.
Under normal conditions, the device is controlled by a program which takes the data input from the above mentioned sensors and decides the degree to which the air being conditioned should be heated or cooled, switches the compressor on and off, determines the setting of the vent doors and the amount of air flow that is induced by the fan.
In the case that a non-automatic or manual mode is required, the vent control button (see FIG. 1) is pressed (once). In response to this, the automatic mode is cancelled and the air conditioner is conditioned to produce a manual mode the initial setting of which is the vent mode. It will be noted that irrespective of the mode that would be induced under automatic control the system always defaults to the vent mode upon the manual mode selection. This feature has been provided in order to enable the occupants to selectively induce very rapid heating and cooling of the cabin.
In the event that the instant mode (i.e. vent mode) is not required or desired, it is possible to select another simply by pressing the vent button again. In the above example, the second depression of the vent button induces the bilevel mode, while the third induces a defrost/foot mode and the fourth induces the defrost mode. A fifth depression toggles back to the vent mode.
However, the order in which the modes are toggled between, is fixed and does not take into account the external air temperature. Accordingly, in the event that the external air temperature is low, it is very likely that the the inner surface of the windshield will undergo rapid fogging or misting. Nevertheless, the air conditioner is arranged to default to the vent mode and the possibility that this fogging will induce reduction in visibility and a consequent loss of driving safety, comes into existence.
Further, if the engine is not yet warmed-up a draft of uncomfortably cold air is apt to be directed against the torso(s) of the passenger(s) seated in the front of the vehicle.